Question

Adeeb bought 5 oranges and 15 apples from the farmer's market. The equation 5r+15a=10.5 represents the amount of money he spent. Faye bought 12 oranges and 11 apples, represented by the equation 12r+11a=11.45 . What was the cost of each apple

Answer 1

Cost of an orange = r
cost of an apple = a

Adeeb bought;
amount of oranges - 5
amount of apples = 15
the equation for the amount he spent 
5r + 15a = 10.5

Faye bought
oranges - 12
apples - 11
the equation for the amount he spent 
12r + 11a = 11.45
set of simultaneous equation
5r + 15a = 10.5 ---> 1)
12r + 11a = 11.45 ---> 2)
divide by the first equation by 5
r + 3a = 2.1--> 3)
Multiply third by 12
12r + 36a = 25.2 ---> 4)
subtract 2nd equation from the 4th
25a = 13.75
a = 0.55
substituting a = 0.55 in 3rd equation 
r + 3*0.55 = 2.1
r = 2.1 - 1.65
r = 0.45
price of an orange = 0.45
price of an apple = 0.55